This invention relates to compositions formulated to improve budbreak, flowering and disease resistance in a variety of trees or crops including perennial fruit crops, to its method of preparation, and to its method of use.
Perennial horticultural and forestry plants native to temperate and boreal regions undergo cyclical periods of active growth and dormancy corresponding to the seasons. When growth resumes in spring the site of new growth is the bud. A dormant bud in a deciduous plant is sometimes called a “winter bud”. Bud dormancy is characterised by a failure to grow even under favourable growth conditions, and the eventual resumption of growth is called dormancy break or “budbreak”. The “depth of dormancy” is directly related to winter chill, which may be measured quantitatively by the accumulation of temperatures below a certain point, e.g. “Richardson Chill Units”, or by average temperatures during the critical late autumn and winter months. Commercial growers working with cultivated plants want to obtain a strong budbreak followed by vigorous growth, flowering (and) fruit production. This occurs naturally when the plants with high chilling requirements experience a cold winter.
Many horticultural regions do not experience cold winters, and changes in local climatic conditions are increasingly exacerbating the problem of poor winter chill. It is possible to overcome the effects of poor winter chill and in some plants or to augment the benefits of good winter chill by chemical treatment of plants in the latter part of dormancy. The simplest chemical “budbreakers” are 4,6-dinitro-o-cresol, now deregulated in most countries, and hydrogen cyanamide (HC), which is still widely used in some countries. In certain crops, e.g. the main “Hayward” kiwifruit variety (Actinidia deliciosa (A. Chev.) C. F. Liang and A. R. Ferguson var. deliciosa), application of HC in late winter dormancy produces almost ideal results:                Increase in % percentage of winter buds that break and develop shoots (% budbreak)        Increase in uniformity of budbreak (i.e. more buds breaking at the same time and rate)        Increase in flower numbers (therefore more fruit at harvest)        Increase in the percentage of shoots bearing flowers (% floral shoots, preferable to increasing flower numbers by increasing the number of flowers per floral shoot)        Condensed flowering (shortened flowering period, coinciding better with flowering of male vines therefore giving better pollination, and resulting in fruit reaching maturity in a synchronous fashion)        Decrease in frequency of naturally occurring double and triple flowers (laterals), which produce undersized or malformed fruit, and must be removed manually at considerable cost to the grower.        Control of green algae and lichen, an additional benefit unrelated to budbreak.        
Unfortunately HC is a very toxic chemical and was excluded from Annex I to Directive 91/414/EEC in October 2008, and its continued use in non-European countries is under threat. The chief concerns are damage to non-target crops and human exposure, which can produce contact dermatitis, respiratory and gastrointestinal tract irritation, headaches, and liver damage when exposure is followed by alcohol consumption. In addition, in some crops HC produces too strong a response and can produce undesirable side effects. For example when applied to yellow-fleshed kiwifruit varieties such Hort16A (Actinidia chinensis Planch. var. chinensis ‘Hort16A’) and Gold3 (Actinidia chinensis Planch. var. chinensis ‘Zesy002’), HC produces too many flowers and increases the frequency of unwanted lateral flowers. Safer budbreakers with more refined activity in plants are clearly needed.